The present invention concerns a single-rod shifting device for a motor vehicle manual transmission, in particular for a six-speed transmission, having a central shifting shaft, having fork-shaped shifting elements in the form of shifting links or thrust forks that engage into sliding bushings, and having a locking device which, upon shifting of one of the shifting elements out of the neutral position into a shifting position, locks in their neutral positions the shifting elements that are not to be shifted.
A single-rod shifting device for a motor vehicle manual transmission having fork-shaped shifting links, engaging into sliding bushings, that can be pivoted by at least one shifting shaft about parallel pivot bearings out of their neutral position into shifting positions, in which context locking means arranged in stationary fashion in the transmission housing coact with locking grooves that are configured in locking links secured to the shifting links in such a way that upon pivoting of one shifting link into a shifting position, the other shifting links are locked in their neutral position, is known from the Applicant""s DE-A 40 17 957. In this, a two-armed rocker arm mounted parallel to the pivot bearing in the transmission housing is arranged in each case between the shifting links, and engages into the locking grooves via end-located blocking cams.
Locking of the shifting links is thus accomplished in this context by means of a rocker-arm and coupling-member system which does not lock the shifting links that are not to be shifted until shifting of a ratio into the selected gate occurs. The lever system comprises three members if three shifting links are provided. In the case of a pure link shifting system, increasing the number of gear ratios in the transmission also increases the number of shifting links, depending on the gear set configuration. If the locking principle were retained, this would require two additional members in the lever system for each additional shifting link. This makes the system complex, difficult to assemble, and sensitive to tolerances; it acts indirectly and is therefore not positive.
A manually shifted transmission for a motor vehicle transmission having a shifting shaft which allows the transmission ratios to be preselected successively by means of its rotation and to be shifted by means of its longitudinal displacement, is known from EP B 530 466. Provided in this is a blocking element, immobilized with the shifting shaft in its longitudinal direction, with which the transmission ratios that are not to be shifted can be locked, the blocking element being a blocking shaft mounted parallel to the shifting shaft, and an entrainment pin of the shifting shaft being longitudinally guided in a gated guide of the blocking shaft in order to transfer the rotary motion. The shifting shaft comprises shifting sleeves on which are rotatably mounted fork sleeves, on which the shifting forks engaging into synchronizer couplings of the transmission ratios are arranged; in order to shift the gear ratios, radially projecting claws of the shifting sleeves rest against the end faces of the fork sleeves, and the claws engage into annular cutouts of the fork sleeves that are not to be actuated.
It is the object of the present invention to create a single-rod shifting device for a motor vehicle manual transmission, in particular for a six-speed transmission, whose locking device is configured in such a way that the shifting elements that are not to be shifted are already locked upon selection of the shift gate, i.e. before the ratio to be shifted is inserted into the selected shifting gate; which is of simple configuration, comprises few parts and thus is easy to assemble; which is configured in terms of function independently of the number of shifting elements and requires little installation space; which locks securely and nevertheless enables good diagonal shiftability; which has low moving masses and low frictional losses, so that there is little influence on selection and shifting forces; and in which the selection of a further ratio is prevented in every case in which a ratio is already selected, and which is economical to manufacture.
Proceeding from a single-rod shifting device of the kind described in more detail above, this object is achieved with the features indicated in the characterizing portion of claim 1; advantageous embodiments are described in the dependent claims.
What is therefore provided according to the present invention is that by way of a radial entrainment, the rotary selection motion of the axially displaceably mounted central shifting shaft is transferred to a lever whose rotation point lies on the rotation axis of the central shifting shaft; that by means of a coupling drive, the rotary motion of the lever is converted into a linear motion of a blocking part transversely to the shifting direction of the central shifting shaft, the blocking part being arranged immovably with respect to the housing in the shifting direction; that the relative motion of the central shifting shaft relative to the blocking part upon shifting of a ratio is accomplished by way of a corresponding degree of freedom in the radial entrainment itself or within the coupling drive; and that the blocking part and the shifting links or thrust forks have blocking elements which are arranged in such a way that upon superposition of the blocking elements in the shifting direction, a motion of the shifting links or thrust forks to shift the transmission ratios is prevented.
The particular advantage achieved thereby is that because of the configuration of the locking device according to the present invention, it is already activated upon selection of the gate, i.e., that the shifting elements which are not to be shifted are already locked before the ratio to be shifted is inserted into the selected gate.